1. Field of the Invention
The present invention generally relates to an apparatus for and method of controlling a vehicle engine, and more particularly, relates to a technique for selecting a combustion mode from a self-ignition combustion mode and a spark ignition combustion mode, during the idling operation of the engine.
2. Description of the Related Art
Hitherto, there has been disclosed in Japanese Unexamined Patent Publications No. 2000-087749 and No. 2000-265873, an engine capable of operating so as to select a combustion mode from a self-ignition combustion mode and a spark ignition combustion mode.
Japanese Unexamined Patent Publication No. 2000-087749 includes therein a description of a technical construction for preventing the self-ignition combustion mode during the time that an engine is still cold and is deteriorated in its stability of the self-ignition combustion mode.
Japanese Unexamined Patent Publication No. 2000-265873 includes therein a description of a technical constitution in which the spark ignition combustion mode is selected during the time that catalyst has not yet been activated in order to direct the flow of the high-temperature exhaust gas obtained by the spark ignition combustion mode toward a catalytic converter to thereby hasten the activity of catalyst.
Although the catalyst can be activated by the spark ignition combustion mode, it is impossible to purify HC (hydrocarbon) and NOx (nitrogen oxide) in the exhaust gas by the catalyst until the catalyst is sufficiently activated. Concerning HC, if appropriate HC adsorbent is disposed in the exhaust passage of an engine, an amount of HC expelled from the engine into the atmosphere might be reduced. However, concerning NOx, there is no effective measure for reducing an amount of NOx expelled into the atmosphere before the catalyst is activated. Therefore, even if spark ignition combustion mode is taken place before the catalyst is activated, it is impossible to satisfactorily reduce expelling of the harmful components of the exhaust gas from the engine into the atmosphere.
Thus, an object of the present invention is to provide an apparatus for and a method of controlling a vehicle engine, which enable it to promote rapid activation of a catalyst as well as to reduce an amount of exhaustion of NOx from the engine before catalyst is activated.
In order to achieve the above-mentioned object, the present invention is constituted such that a combustion made is selected from a self-ignition combustion mode and a spark ignition combustion mode based on a temperature Te of a vehicle engine and a temperature Tc of a catalyst, to control the engine according to the selected combustion mode when the engine is in idling operation,
The other objects and features of the present invention will become understood from the following description of a preferred embodiment thereof with reference to the accompanying drawings.